PROJECT #1: SUMMARY/ABSTRACT It is now clear that the latent reservoir constitutes the major barrier to a sterilizing cure for HIV, and that the development of novel, paradigm-shifting approaches will likely be required for successful long-term viral control. Recently, hematopoietic stem cell transplantation (HCT) has offered some promise of a cure, but continues to contain significant challenges. The Berlin Patient, who received an allogeneic HCT (allo-HCT) with HIV-resistant cells, is the only patient cured of HIV. This finding has stimulated an intense investigation as to the components of HCT that contributed to his cure. These components include: (1) Pre-transplant conditioning; (2) Transplantation with allogeneic cells; (3) The development of GVHD; and (4) Transplant with HIV-resistant donor cells. The Berlin patient had all 4 components, while the Boston patients lacked intense conditioning and resistant cells. The viral rebound observed in the Boston patients but not in the Berlin patient forms the foundational observation upon which this proposal is based: Our goal is to systematically investigate each of the four transplant components described above and determine their impact on HIV eradication. While the critical elements of the Berlin patient's transplant have not yet been determined, it is clear that the success of any treatment modality will be directly related to its ability to clear the HIV reservoir. However, a comprehensive anatomic, cellular and temporal map of the HIV reservoir as it is impacted by transplantation does not yet exist. Thus, the creation of a detailed map of reservoir sites, as they are impacted by transplantation, and prior to cART interruption, represents a critical unmet need in the field. This need is exceedingly difficult to address in patients, given clinical limitations on tissue sampling and intensive longitudinal analysis. Therefore, to address this need, we will use the powerful pig-tail macaque model of transplantation and SHIV infection that has been established by our group, to create a detailed map of the HIV reservoir as it is impacted by transplantation, and will then use this map to enable an evidence-based approach to cART interruption after transplant. We will accomplish this through the following Specific Aims: (1) To create an anatomic, cellular and temporal map of transplant-resistant sanctuary sites after auto-HCT with gene-modified, SHIV-resistant hematopoietic stem cells (HSCs); and (2) To determine the ability of allo-HCT, with and without SHIV-resistant cells, to clear the viral reservoir. The successful completion of these Aims will fundamentally deepen our understanding of the cellular and immunologic components of the viral reservoir, and will establish novel transplant?based strategies for HIV eradication.